The blockquote colour... The best way to see how to do it is use your browser's View menu which should contain a Page Source option. When you can see the source, scroll down (or use search) till you get to the text in the box. You'll see the html involved is a div rather than a blockquote. Copy it into a .txt file (for example) for handy use.

As for colour, you'll see the "color" setting in the div code chunk. To change colour, try this code page. Pick a colour and copy in its code or name. Here is a page where you can try out colour codes as background. The code is composed of three hexadecimal numbers representing Red, Green, Blue. The higher the value, the more you tend towards white, so, if you find a colour is too dark for background, raise the values and try again.

When you've found the one you like, save it with your div code for future use in diaries, or comments... Though I think in comments blockquote will be a handy quick choice for me...